The purpose of this study was to determine the effects of Red Bull energy drink on Wingate cycle performance and muscle endurance. Healthy young adults (N = 15, 11 men, 4 women, 21 ± 5 y old) participated in a crossover study in which they were randomized to supplement with Red Bull (2 mg/kg body mass of caffeine) or isoenergetic, isovolumetric, noncaffeinated placebo, separated by 7 d. Muscle endurance (bench press) was assessed by the maximum number of repetitions over 3 sets (separated by 1-min rest intervals) at an intensity corresponding to 70% of baseline 1-repetition maximum. Three 30-s Wingate cycling tests (load = 0.075 kp/kg body mass), with 2 min recovery between tests, were used to assess peak and average power output. Red Bull energy drink significantly increased total bench-press repetitions over 3 sets (Red Bull = 34 ± 9 vs. placebo = 32 ± 8, P < 0.05) but had no effect on Wingate peak or average power (Red Bull = 701 ± 124 W vs. placebo = 700 ± 132 W, Red Bull = 479 ± 74 W vs. placebo = 471 ± 74 W, respectively). Red Bull energy drink significantly increased upper body muscle endurance but had no effect on anaerobic peak or average power during repeated Wingate cycling tests in young healthy adults.
Scott C. Forbes, Darren G. Candow, Jonathan P. Little, Charlene Magnus and Philip D. Chilibeck
Darren G. Burke, Philip D. Chilibeck, Gianni Parise, Mark A. Tarnopolsky and Darren G. Candow
α-lipoic acid has been found to enhance glucose uptake into skeletal muscle in animal models. Studies have also found that the co-ingestion of carbohydrate along with creatine increases muscle creatine uptake by a process related to insulin-stimulated glucose disposal. The purpose of this study was to determine the effect of α-lipoic acid on human skeletal muscle creatine uptake by directly measuring intramuscular concentrations of creatine, phosphocreatine, and ad-enosine triphosphate when creatine monohydrate was co-ingested with α-lipoic acid. Muscle biopsies were acquired from the vastus lateralis m. of 16 male subjects (18–32 y) before and after the experimental intervention. After the initial biopsy, subjects ingested 20 g · d−1 of creatine monohydrate, 20 g · d−1 of creatine monohydrate + 100 g · d−1 of sucrose, or 20 g · d−1 of creatine monohydrate + 100 g · d−1 of sucrose + 1000 mg · d−1 of α-lipoic acid for 5 days. Subjects refrained from exercise and consumed the same balanced diet for 7 days. Body weight increased by 2.1% following the nutritional intervention, with no differences between the groups. There was a significant increase in total creatine concentration following creatine supplementation, with the group ingesting α-lipoic acid showing a significantly greater increase (p < .05) in phosphocreatine (87.6 → 106.2 mmol · kg−1 dry mass [dm]) and total creatine (137.8 → 156.8 mmol · kg−1 dm). These findings indicate that co-ingestion of α-lipoic acid with creatine and a small amount of sucrose can enhance muscle total creatine content as compared to the ingestion of creatine and sucrose or creatine alone.
Jonathan. P. Little, Scott C. Forbes, Darren G. Candow, Stephen M. Cornish and Philip D. Chilibeck
Creatine (Cr) supplementation increases muscle mass, strength, and power. Arginine α-ketoglutarate (A-AKG) is a precursor for nitric oxide production and has the potential to improve blood flow and nutrient delivery (i.e., Cr) to muscles. This study compared a commercial dietary supplement of Cr, A-AKG, glutamine, taurine, branchedchain amino acids, and medium-chain triglycerides with Cr alone or placebo on exercise performance and body composition. Thirty-five men (~23 yr) were randomized to Cr + A-AKG (0.1 g · kg−1 · d−1 Cr + 0.075 g · kg−1 · d−1 A-AKG, n = 12), Cr (0.1 g · kg−1 · d−1, n = 11), or placebo (1 g · kg−1 · d−1 sucrose, n = 12) for 10 d. Body composition, muscle endurance (bench press), and peak and average power (Wingate tests) were measured before and after supplementation. Bench-press repetitions over 3 sets increased with Cr + A-AKG (30.9 ==6.6 → 34.9 ± 8.7 reps; p < .01) and Cr (27.6 ± 5.9 → 31.0 ± 7.6 reps; p < .01), with no change for placebo (26.8 ± 5.0 → 27.1 ± 6.3 reps). Peak power significantly increased in Cr + A-AKG (741 ± 112 → 794 ± 92 W; p < .01), with no changes in Cr (722 ± 138 → 730 ± 144 W) and placebo (696 ± 63 → 705 ± 77 W). There were no differences in average power between groups over time. Only the Cr-only group increased total body mass (79.9 ± 13.0→81.1 ± 13.8 kg; p < .01), with no significant changes in lean-tissue or fat mass. These results suggest that Cr alone and in combination with A-AKG improves upper body muscle endurance, and Cr + A-AKG supplementation improves peak power output on repeated Wingate tests.
Jonathan P. Little, Philip D. Chilibeck, Dawn Ciona, Albert Vandenberg and Gordon A. Zello
The glycemic index (GI) of a pre exercise meal may affect substrate utilization and performance during continuous exercise.
To examine the effects of low- and high-GI foods on metabolism and performance during high-intensity, intermittent exercise.
Seven male athletes participated in three experimental trials (low-GI, high-GI, and fasted control) separated by ~7 days. Foods were consumed 3 h before (~1.3 g·kg−1 carbohydrate) and halfway through (~0.2 g·kg−1 carbohydrate) 90 min of intermittent treadmill running designed to simulate the activity pattern of soccer. Expired gas was collected during exercise to estimate substrate oxidation. Performance was assessed by the distance covered on fve 1-min sprints during the last 15 min of exercise.
Respiratory exchange ratio was higher and fat oxidation lower during exercise in the high-GI condition compared with fasting (P < .05). The mean difference in total distance covered on the repeated sprint test between low GI and fasting (247 m; 90% confidence limits ±352 m) represented an 81% (likely, probable) chance that the low-GI condition improved performance over fasting. The mean difference between high GI and fasted control (223 m; ±385 m) represented a 76% (likely, probable) chance of improved performance. There were no differences between low and high GI.
When compared with fasting, both low- and high-GI foods consumed 3 h before and halfway through prolonged, high-intensity intermittent exercise improved repeated sprint performance. High-GI foods impaired fat oxidation during exercise but the GI did not appear to influence high-intensity, intermittent exercise performance.
Darren G. Burke, Darren G. Candow, Philip D. Chilibeck, Lauren G. MacNeil, Brian D. Roy, Mark A. Tarnopolsky and Tim Ziegenfuss
The purpose of this study was to compare changes in muscle insulin-like growth factor-I (IGF-I) content resulting from resistance-exercise training (RET) and creatine supplementation (CR). Male (n = 24) and female (n = 18) participants with minimal resistance-exercise-training experience (≥1 year) who were participating in at least 30 min of structured physical activity (i.e., walking, jogging, cycling) 3–5 ×/wk volunteered for the study. Participants were randomly assigned in blocks (gender) to supplement with creatine (CR: 0.25 g/kg lean-tissue mass for 7 days; 0.06 g/kg lean-tissue mass for 49 days; n = 22, 12 males, 10 female) or isocaloric placebo (PL: n = 20, 12 male, 8 female) and engage in a whole-body RET program for 8 wk. Eighteen participants were classified as vegetarian (lacto-ovo or vegan; CR: 5 male, 5 female; PL: 3 male, 5 female). Muscle biopsies (vastus lateralis) were taken before and after the intervention and analyzed for IGF-I using standard immunohistochemical procedures. Stained muscle cross-sections were examined microscopically and IGF-I content quantified using image-analysis software. Results showed that RET increased intramuscular IGF-I content by 67%, with greater accumulation from CR (+78%) than PL (+54%; p = .06). There were no differences in IGF-I between vegetarians and nonvegetarians. These findings indicate that creatine supplementation during resistance-exercise training increases intramuscular IGF-I concentration in healthy men and women, independent of habitual dietary routine.
Whitney R.D. Duff, Philip D. Chilibeck, Julianne J. Rooke, Mojtaba Kaviani, Joel R. Krentz and Deborah M. Haines
Bovine colostrum is the first milk secreted by cows after parturition and has high levels of protein, immunoglobulins, and various growth factors. We determined the effects of 8 weeks of bovine colostrum supplementation versus whey protein during resistance training in older adults. Males (N = 15, 59.1 ± 5.4 y) and females (N = 25, 59.0 ± 6.7 y) randomly received (double-blind) 60g/d of colostrum or whey protein complex (containing 38g protein) while participating in a resistance training program (12 exercises, 3 sets of 8–12 reps, 3 days/week). Strength (bench press and leg press 1-RM), body composition (by dual energy x-ray absorptiometry), muscle thickness of the biceps and quadriceps (by ultrasound), cognitive function (by questionnaire), plasma insulin-like growth factor-1 (IGF-1) and C-reactive protein (CRP, as a marker of inflammation), and urinary N-telopeptides (Ntx, a marker of bone resorption) were determined before and after the intervention. Participants on colostrum increased leg press strength (24 ± 29 kg; p < .01) to a greater extent than participants on whey protein (8 ± 16 kg) and had a greater reduction in Ntx compared with participants on whey protein (–15 ± 40% vs. 10 ± 42%; p < .05). Bench press strength, muscle thickness, lean tissue mass, bone mineral content, and cognitive scores increased over time (p < .05) with no difference between groups. There were no changes in IGF-1 or CRP. Colostrum supplementation during resistance training was beneficial for increasing leg press strength and reducing bone resorption in older adults. Both colostrum and whey protein groups improved upper body strength, muscle thickness, lean tissue mass, and cognitive function.
Jonathan P. Little, Philip D. Chilibeck, Dawn Ciona, Scott Forbes, Huw Rees, Albert Vandenberg and Gordon A. Zello
Consuming carbohydrate-rich meals before continuous endurance exercise improves performance, yet few studies have evaluated the ideal preexercise meal for high-intensity intermittent exercise, which is characteristic of many team sports. The authors’ purpose was to investigate the effects of low- and high-glycemic-index (GI) meals on metabolism and performance during high-intensity, intermittent exercise. Sixteen male participants completed three 90-min high-intensity intermittent running trials in a single-blinded random order, separated by ~7 d, while fasted (control) and 2 hr after ingesting an isoenergetic low-GI (lentil), or high-GI (potato and egg white) preexercise meal. Serum free fatty acids were higher and insulin lower throughout exercise in the fasted condition (p < .05), but there were no differences in blood glucose during exercise between conditions. Distance covered on a repeated-sprint test at the end of exercise was significantly greater in the low-GI and high-GI conditions than in the control (p < .05). Rating of perceived exertion was lower in the low-GI condition than in the control (p = .01). In a subsample of 5 participants, muscle glycogen availability was greater in the low- and high-GI conditions versus fasted control before the repeated-sprint test (p < .05), with no differences between low and high GI. When exogenous carbohydrates are not provided during exercise both low- and high-GI preexercise meals improve high-intensity, intermittent exercise performance, probably by increasing the availability of muscle glycogen. However, the GI does not influence markers of substrate oxidation during high-intensity, intermittent exercise.
Darren G. Burke, Shawn Silver, Laurence E. Holt, Truis Smith-Palmer, Christopher J. Culligan and Philip D. Chilibeck
Dietary supplementation (SUP) has become a significant part of athletic training. Studies indicate that creatine (Cr) can enhance short-duration, high-intensity activities. This study examined the effect of 21 days of low dose Cr SUP (~7.7 g/day) and resistance training on force output, power output, duration of mean peak power output, and total work performed until fatigue. A double-blind protocol was used, where an individual, who was not part of any other aspect of the study, randomly assigned subjects to creatine and placebo groups. Forty-one male university athletes were randomly assigned to either Cr (n= 20) or placebo (n = 21) SUP. On the first and last day of the study, subjects were required to perform concentric bench press movements until exhaustion on an isokinetic dynamometer. The dynamometer was hard-wired to a personal computer, which provided force, velocity, and duration measures. Force and power output until fatigue, were used to determine total work, force-time, and power-time relationships. ANOVA results revealed that the Cr subjects performed more total work until fatigue, experienced significantly greater improvements in peak force and peak power, and maintained elevated mean peak power for a longer period of time. These results indicate that Cr SUP can significantly improve factors associated with short-duration, high-intensity activity.
Darren G. Burke, Philip D. Chilibeck, K. Shawn Davison, Darren C. Candow, Jon Farthing and Truis Smith-Palmer
Our purpose was to assess muscular adaptations during 6 weeks of resistance training in 36 males randomly assigned to supplementation with whey protein (W; 1.2 g/kg/day), whey protein and creatine monohydrate (WC; 0.1 g/kg/day), or placebo (P; 1.2 g/kg/day maltodextrin). Measures included lean tissue mass by dual energy x-ray absorptiometry, bench press and squat strength (1-repetition maximum), and knee extension/flexion peak torque. Lean tissue mass increased to a greater extent with training in WC compared to the other groups, and in the W compared to the P group (p < .05). Bench press strength increased to a greater extent for WC compared to W and P (p < .05). Knee extension peak torque increased with training for WC and W (p < .05), but not for P. All other measures increased to a similar extent across groups. Continued training without supplementation for an additional 6 weeks resulted in maintenance of strength and lean tissue mass in all groups. Males that supplemented with whey protein while resistance training demonstrated greater improvement in knee extension peak torque and lean tissue mass than males engaged in training alone. Males that supplemented with a combination of whey protein and creatine had greater increases in lean tissue mass and bench press than those who supplemented with only whey protein or placebo. However, not all strength measures were improved with supplementation, since subjects who supplemented with creatine and/or whey protein had similar increases in squat strength and knee flexion peak torque compared to subjects who received placebo.
Darren G. Candow, Philip D. Chilibeck, Karen E. Chad, Murray J. Chrusch, K. Shawn Davison and Darren G. Burke
The authors previously found that creatine (Cr) combined with 12 weeks of resistance training enhanced muscle strength and endurance and lean tissue mass (LTM) in older men. Their purpose in this study was to assess these variables with cessation of Cr combined with 12 weeks of reduced training (33% lower volume) in a subgroup of these men (n = 8, 73 years old) compared with 5 men (69 years old) who did not receive Cr. Strength (1-repetition maximum [1-RM]), endurance (maximum number of repetitions over 3 sets at 70–80% 1-RM), and LTM (dual-energy X-ray absorptiometry) were assessed before and after 12 weeks of Cr cessation combined with reduced-volume training. No changes in strength or LTM occurred. Muscle endurance was significantly reduced (7–21%; p < .05), with the rate of change similar between groups. Withdrawal from Cr had no effect on the rate of strength, endurance, and loss of lean tissue mass with 12 weeks of reduced-volume training.